In my U.S. Pat. No. 4,398,994, I have described in continuous method of forming decorative patterns of aluminized plastic film and the use of such patterned film in packaging. As is described therein, a web of aluminized polymer film is printed with a pattern of etchant-resistant material, corresponding to the pattern desired on the aluminized surface. Aqueous sodium hydroxide solution having a concentration of up to about 25 wt. % is applied, at a temperature of about 15.degree. to about 100.degree. C., across the whole width of the web to contact the pattern on the web. The sodium hydroxide solution is allowed to remain in contact with the web as it is conveyed for about 0.1 to about 10 seconds to permit the sodium hydroxide to dissolve aluminum only from areas of the web not having the pattern of etchant-resistant material applied thereto. The spent sodium hydroxide solution is washed from the web to leave the pattern of etchant-resistant material on the transparent polymeric film. The various steps of the operation are effected consecutively at a web speed of up to about 1000 ft/min.
The apparatus illustrated in the aforementioned patent utilizes rollers dipping into baths of liquid to effect the various steps. This manner of application of etchant and of wash water has been found to be somewhat inefficient in ensuring a consistent product at high speeds of operation and also is uneconomical with respect to utilization of sodium hydroxide etchant.